SERVER-63002 Support bindata types for variants in IDL

3 files changed, 83 insertions, 37 deletions

diff --git a/buildscripts/idl/idl/binder.py b/buildscripts/idl/idl/binder.py
index d615f4a633b..49fab8a39e1 100644
--- a/buildscripts/idl/idl/binder.py
+++ b/buildscripts/idl/idl/binder.py
@@ -87,15 +87,15 @@ def _validate_bson_types_list(ctxt, idl_type, syntax_type):
             ctxt.add_bad_bson_type_error(idl_type, syntax_type, idl_type.name, bson_type)
             return False
 
-        # V1 restiction: cannot mix bindata into list of types
-        if bson_type == "bindata":
-            ctxt.add_bad_bson_type_error(idl_type, syntax_type, idl_type.name, bson_type)
-            return False
+        if not isinstance(idl_type, syntax.VariantType):
+            if bson_type == "bindata":
+                ctxt.add_bad_bson_type_error(idl_type, syntax_type, idl_type.name, bson_type)
+                return False
 
-        # Cannot mix non-scalar types into the list of types
-        if not isinstance(idl_type, syntax.VariantType) and not bson.is_scalar_bson_type(bson_type):
-            ctxt.add_bad_bson_scalar_type_error(idl_type, syntax_type, idl_type.name, bson_type)
-            return False
+            # Cannot mix non-scalar types into the list of types
+            if not bson.is_scalar_bson_type(bson_type):
+                ctxt.add_bad_bson_scalar_type_error(idl_type, syntax_type, idl_type.name, bson_type)
+                return False
 
     return True
 
diff --git a/buildscripts/idl/idl/generator.py b/buildscripts/idl/idl/generator.py
index d9879e97109..ff9da001069 100644
--- a/buildscripts/idl/idl/generator.py
+++ b/buildscripts/idl/idl/generator.py
@@ -30,6 +30,7 @@
 
 import hashlib
 import io
+import itertools
 import os
 import re
 import sys
@@ -1962,11 +1963,26 @@ class _CppSourceFileWriter(_CppFileWriterBase):
         }
 
         with self._with_template(template_params):
-            # See https://en.cppreference.com/w/cpp/utility/variant/visit
-            # This lambda is a template instantiated for each alternate type. Use "if constexpr"
-            # to compile the appropriate serialization code for each.
-            with self._block('stdx::visit([builder](auto&& arg) {', '}, ${access_member});'):
-                self._writer.write_template('idl::idlSerialize(builder, ${field_name}, arg);')
+            with self._block('stdx::visit(visit_helper::Overloaded{', '}, ${access_member});'):
+                for variant_type in itertools.chain(
+                        field.type.variant_types,
+                    [field.type.variant_struct_type] if field.type.variant_struct_type else []):
+
+                    template_params[
+                        'cpp_type'] = 'std::vector<' + variant_type.cpp_type + '>' if variant_type.is_array else variant_type.cpp_type
+
+                    with self._block('[builder](const ${cpp_type}& value) {', '},'):
+                        bson_cpp_type = cpp_types.get_bson_cpp_type(variant_type)
+                        if bson_cpp_type and bson_cpp_type.has_serializer():
+                            assert not field.type.is_array
+                            expression = bson_cpp_type.gen_serializer_expression(
+                                self._writer, 'value')
+                            template_params['expression'] = expression
+                            self._writer.write_template(
+                                'builder->append(${field_name}, ${expression});')
+                        else:
+                            self._writer.write_template(
+                                'idl::idlSerialize(builder, ${field_name}, value);')
 
     def _gen_serializer_method_common(self, field):
         # type: (ast.Field) -> None
@@ -2604,10 +2620,9 @@ class _CppSourceFileWriter(_CppFileWriterBase):
 
         # Generate mongo includes third
         header_list = [
-            'mongo/bson/bsonobjbuilder.h',
-            'mongo/db/auth/authorization_contract.h',
-            'mongo/db/commands.h',
-            'mongo/idl/command_generic_argument.h',
+            'mongo/bson/bsonobjbuilder.h', 'mongo/db/auth/authorization_contract.h',
+            'mongo/db/commands.h', 'mongo/idl/command_generic_argument.h',
+            'mongo/util/visit_helper.h'
         ]
 
         if spec.server_parameters:
diff --git a/buildscripts/idl/tests/test_binder.py b/buildscripts/idl/tests/test_binder.py
index 47f6d62efa4..b1f809ff5c7 100644
--- a/buildscripts/idl/tests/test_binder.py
+++ b/buildscripts/idl/tests/test_binder.py
@@ -602,6 +602,57 @@ class TestBinder(testcase.IDLTestcase):
                         foo: array<int>
             """))
 
+    def test_variant_positive(self):
+        # type: () -> None
+        """Positive variant test cases."""
+
+        # Setup some common types
+        test_preamble = textwrap.dedent("""
+        types:
+            string:
+                description: foo
+                cpp_type: foo
+                bson_serialization_type: string
+                serializer: foo
+                deserializer: foo
+                default: foo
+            int:
+                description: foo
+                cpp_type: std::int32_t
+                bson_serialization_type: int
+                deserializer: mongo::BSONElement::_numberInt
+            bindata_function:
+                bson_serialization_type: bindata
+                bindata_subtype: function
+                description: "A BSON bindata of function sub type"
+                cpp_type: "std::vector<std::uint8_t>"
+                deserializer: "mongo::BSONElement::_binDataVector"
+        """)
+
+        self.assert_bind(test_preamble + textwrap.dedent("""
+        structs:
+            foo:
+                description: foo
+                fields:
+                    my_variant_field:
+                        type:
+                            variant:
+                            - string
+                            - int
+            """))
+
+        self.assert_bind(test_preamble + textwrap.dedent("""
+        structs:
+            foo:
+                description: foo
+                fields:
+                    my_variant_field:
+                        type:
+                            variant:
+                            - string
+                            - bindata_function
+            """))
+
     def test_variant_negative(self):
         # type: () -> None
         """Negative variant test cases."""
@@ -637,12 +688,6 @@ class TestBinder(testcase.IDLTestcase):
                 description: foo
                 cpp_type: "std::int32_t"
                 deserializer: "mongo::BSONElement::safeNumberInt"
-            bindata_function:
-                bson_serialization_type: bindata
-                bindata_subtype: function
-                description: "A BSON bindata of function sub type"
-                cpp_type: "std::vector<std::uint8_t>"
-                deserializer: "mongo::BSONElement::_binDataVector"
         """)
 
         self.assert_bind_fail(
@@ -685,20 +730,6 @@ class TestBinder(testcase.IDLTestcase):
                         default: 1
             """), idl.errors.ERROR_ID_VARIANT_NO_DEFAULT)
 
-        # Bindata is banned in variants for now.
-        self.assert_bind_fail(
-            test_preamble + textwrap.dedent("""
-        structs:
-            foo:
-                description: foo
-                fields:
-                    my_variant_field:
-                        type:
-                            variant:
-                            - string
-                            - bindata_function
-            """), idl.errors.ERROR_ID_BAD_BSON_TYPE)
-
         # Enums are banned in variants for now.
         self.assert_bind_fail(
             test_preamble + textwrap.dedent("""